Tesla has moved beyond the electric car market, creating a battery farm to store energy for the Southern California Edison power company – the largest it has ever built for a power company. The farm, located at the power company’s Mira Loma substation in Ontario, California, has a 20 megawatt capacity, built to discharge 80-megawatt hours of electricity in four-hour periods. The farm includes enough batteries to power roughly 1,000 Tesla vehicles, and can power about 15,000 homes for four hours.

Such battery systems allow power companies to store surplus electricity from natural gas, solar, or wind power, and have it available when power plants are unable to cover any spikes in demand. The development of these batteries is an area of expertise for Tesla, which markets the batteries as a way to store solar power for after sundown.

After a leak occurred at the Aliso Canyon natural gas reservoir near Los Angeles in 2015, forcing thousands to evacuate the area, Edison hired Tesla and other companies to build the new battery farms. The leak had become a large-scale environmental disaster, sending high quantities of methane, a heat trapping greenhouse gas, into the atmosphere. The closing of the reservoir meant power companies needed to find a new way to manage short-term spikes in energy demand.

In order to solve this problem, the California Public Utilities Commission approved projects to store 100 megawatts of energy for Southern California Edison and also San Diego Gas & Electric, meant to be completed before the end of 2016. The Tesla project is one of several meant to address this problem. Even before the Aliso Canyon incident, the Utilities Commission had expected energy storage like the Tesla project to become important to California’s plan to transition to renewable energy. The Commission has set an energy storage target of 1,325 megawatts for 2020.

Kevin Payne, CEO of Southern California Edison said at the project’s ribbon-cutting ceremony on Monday, that the Tesla project “validates that energy storage can be part of the energy mix now” and represents “a great reminder of how fast technology is changing the electric power industry.”

The recent wave of energy storage projects uses newer versions of lithium-ion batteries, once prohibitively expensive, but now made cheaper thanks to mass production by companies such as Samsung, Panasonic, and Tesla. The prices of such batteries have been reported have dropped as much as 70 percent in the last two years, according to companies who buy them.

Tesla considers energy storage to be a way to move beyond the electric car market. Tesla CEO Elon Musk has indicated that this aspect of Tesla could one day outstrip its electric car business.